GEOMETRIC MORPHOMETRICS IN PRIMATOLOGY - CRANIOFACIAL VARIATION IN HOMO-SAPIENS AND PAN-TROGLODYTES

Traditionally, morphometric studies have relied on statistical analysi s of distances, angles or ratios to investigate morphometric variation among taxa. Recently, geometric techniques have been developed for th e direct analysis of landmark data. In this paper, we offer a summary (with examples) of three of these newer techniques, namely shape coord inate, thin-plate spline and relative warp analyses. Shape coordinate analysis detected significant craniofacial variation between 4 modem h uman populations, with African and Australian Aboriginal specimens bei ng relatively prognathous compared with their Eurasian counterparts. I n addition, the Australian specimens exhibited greater basicranial fle xion than all other samples. The observed relationships between size a nd craniofacial shape were weak. The decomposition of shape variation into affine and non-affine components is illustrated via a thin-plate spline analysis of Homo and Pan cranial landmarks. We note differences between Homo and Pan in the degree of prognathism and basicranial fle xion and the position and orientation of the foramen magnum. We compar e these results with previous studies of these features in higher prim ates and discuss the utility of geometric morphometrics as a tool in p rimatology and physical anthropology. We conclude that many studies of morphological variation, both within and between taxa, would benefit from the graphical nature of these techniques.